The description of structure implicitly offers an account of what a system is made of: a configuration of items, a collection of inter-related components or services. A structure may be a hierarchy (a cascade of one-to-many relationships), a network featuring many-to-many links, or a lattice featuring connections between components that are neighbors in space.

In engineering and architecture, a structure is a body or assemblage of bodies in space to form a system capable of supporting loads. Physical structures include man-made and natural arrangements. Buildings, aircraft, soap films, skeletons, anthills, beaver dams and salt domes are all examples of physical structures. The effects of loads on physical structures are determined through structural analysis. Structural engineering refers to engineering of physical structures.

Chemistry is a science that treats matter at the atomic to macromolecular scale—the reactions, transformations, and aggregations of matter, and accompanying energy and entropy changes in these processes. Chemical structure refers to both molecular geometry and electronic structure. The structural formula of a chemical compound is a graphical representation of the molecular structure that shows how the atoms are arranged. A protein structure is the three-dimensional coordinates of the atoms within (macro) molecules made of protein.

A social structure is a pattern of relationships. They are social organizations of individuals in various life situations. Structures are applicable to people in how a society is as a system organized by a characteristic pattern of relationships. This is known as the social organization of the group. Sociologists have studied the changing structure of these groups. Structure and agency are two confronted theories about human behaviour. The debate surrounding the influence of structure and agency on human thought is one of the central issues in sociology. In this context, agency refers to the individual human capacity to act independently and make free choices. Structure here refers to factors such as social class, religion, gender, ethnicity, customs etc. that seem to limit or influence individual opportunities.

In computer science, a data structure is a way of storing data in a computer so that it can be used efficiently. Often a carefully chosen data structure facilitates using the most efficientalgorithm. The choice of the data structure often begins from the choice of an abstractdata type. A well-designed data structure supports a variety of critical operations using as few resources (execution time and memory space) as possible. Data structures are implemented in a programming language as data types and the references (e.g. relationships, links and pointers) and operations that are possible with them. For structure tables and structure functions, see data structure.

Software architecture is the act of choosing and excluding specific structural options from possibilities in the design of software. This decision requires the application of principles tailored to serve the purposes of the software. For example: the systems that controlled the space shuttle launch vehicle have the requirement of being very fast, and very reliable, in principle. Therefore an interpretive language, which is traditionally slow compared to a machine code program, would be excluded from the space shuttle control system software architecture; and multiple redundant copies running on independent hardware and cross-checking results would be a software system architectural choice to satisfy the need for reliability. Therefore software architecture is about making structural choices, which are costly to change once implemented.